1. Field of the Invention
The invention is directed to purified and isolated polypeptides, the nucleic acids encoding the polypeptides, and processes for production of recombinant forms of the polypeptides. This invention is also directed to antibodies that specifically recognize the polypeptides, compositions containing the polypeptides, and to the use of these materials in various assays. In particular, the polypeptides, the nucleic acids encoding the polypeptides, and the antibodies are useful for the detection of human B cell lymphomas, enhancing the production of interferon γ (IFN-γ), enhancing the growth of NK cells, treating viral infections and tumors, and enhancing the activity of cytotoxic T lymphocytes (CTLs).
2. Description of Related Art
1. Lymphomas
The malignant lymphomas represent multiple diseases with diverse morphologic and clinical expressions. Morphologic classification schemes have been shown to be useful in delineating natural history, prognosis, and response to therapy. However, in some instances, distinctive morphologic entities may be very closely related clinically or biologically or both, whereas other diseases that share morphologic similarities may be clinically and biologically quite distinct. Thus, immunological methods have become essential tools for the diagnosis and classification of certain human tumors, particularly for leukemias and lymphomas.
More particularly, some patients carrying malignancies have been found to produce antibodies against tumor-associated or other malignant cell-associated surface determinants as well as against a variety of differentiation and other non-tumor antigens. Several very sensitive immunological procedures have been developed for the detection of such antibodies.
A variety of other markers of hematopoietic malignancies allows clinically valuable categorizations, which are not possible by morphological or histochemical parameters. These markers can also be detected using immunological procedures. One of the main advantages of these procedures over other methods for the measurement of tumor-associated markers is their high level of sensitivity, with the ability often to detect a substance at nanogram or even picogram levels. In addition, immunological tests afford the ability to discriminate among substances with closely related structures and thereby to identify tumor-associated analogs found in normal, nonmalignant states.
Many tumor-associated markers have been detected in the sera or other body fluids of patients with malignancies. A few of these markers have been sufficiently restricted to tumor-bearing individuals to aid in detection or differential diagnosis (or both) of malignant disease. However, most markers have been found to lack sufficient specificity for such applications, with an appreciable frequency of elevated marker levels in patients with nonmalignant diseases (i.e., false positive results).
In addition, malignant lymphomas are usually an admixture of a neoplastic element and normal elements or both. A cell suspension prepared from a malignant lymphoma will consist of a mixture of benign and malignant cells, and the malignant cells may not necessarily be in the majority. To determine the phenotype of malignant cells, it is necessary to identify those markers associated with neoplastic cells.
It should be evident that there exists a need in the art for the identification of additional cell surface markers associated with malignant conditions. In particular, there is a continuing need for cell surface markers associated with malignant lymphomas. The identification of specific cell surface markers associated with malignant lymphomas will aid the detection of malignancies associated with these markers.
2. NK Cells
One of the major types of circulating mononuclear cells is that of the natural killer, or NK, cell (M. Manoussaka et al., Journal of Immunology 158:112-119, 1997). NK cells are a cell type derived from bone marrow precursors (O. Haller et al., Journal of Experimental Medicine 145:1411-1420, 1977). NK cells appear to be closely related to T cells and the two cell types share many cell surface markers (M. Manoussaka et al., 1997). Although NK cells are cytotoxic cells as are some T cells, unlike T cells, NK cells do not express the T-cell receptor or CD3 components (P. Scott and G. Trinichieri, Current Opinion in Immunology 7:34-40, 1995; G. Trinichieri, Adv. Immunology 47:187-376, 1989). NK cells commonly express CD16 and CD56 antigens (K. Oshimi, International Journal of Hematology 63:279-290, 1996). Similar to cytotoxic T lymphocytes (CTL), NK cells are capable of exerting a cytotoxic effect by lysing a variety of cell types (G. Trinichieri, 1989). NK cells are capable of exerting cytotoxicity in a non-MHC restricted fashion (E. Ciccione et al., J. Exp. Med. 172:47, 1990; A. Moretta et al., J. Exp. Med. 172:1589, 1990; and E. Ciccione et al., J. Exp. Med. 175:709).
NK cells mediate some of their functions through the secretion of cytokines, such as interferon γ (IFNγ), granulocyte-macrophage colony-stimulating factors (GM-CSFs), tumor necrosis factor α (TNF-α), macrophage colony-stimulating factor (M-CSF), interleukin-3 (IL-3), and IL-8 (P. Scott and G. Trinichieri, 1995).
Cytokines including IL-2, IL-12, TNF-α and IL-1 can induce NK cells to produce cytokines (P. Scott and G. Trinichieri, 1995). IFNγ and IL-2 are strong inducers of NK cell cytotoxic activity (G. Trinichieri et al., Journal of Experimental Medicine 160:1147-1169, 1984; G. Trinichieri and D. Santoli, Journal of Experimental Medicine 147:1314-1333, 1977). NK cells can be stimulated and expanded in the presence of IL-2 (K. Oshimi, International Journal of Hematology 63:279-290, 1996). IL-12 has been shown to induce cytokine production from T and NK cells, and augment NK cell-mediated cytotoxicity (M. Kobayashi et al., Journal of Experimental Medicine 170:827-846, 1989).
NK cells can lyse a variety of cell types, including normal stem cells, infected cells, and transformed cells (D. See et al., Scand. J. Immunol. 46:217-224, 1997). Cells that lack MHC class I are susceptible to NK cell-mediated lysis (H. Reyburn et al., Immunol. Rev. 155:119-125, 1997). The lysis of cells occurs through the action of cytoplasmic granules containing proteases, nucleases, and perforin (D. See et al., 1997). Antibodies directed against CD2 and CD11a inhibit the cytotoxic effect of NK cells (O. Ramos et al., J. Immunol. 142:4100-4104, 1989; C. Scott et al., J. Immunol. 142:4105-4112, 1989). NK cells can also lyse cells by antibody-dependent cellular cytotoxicity (D. See et al., 1997).
NK cells have been shown to destroy both extracellular protozoa and the cells infected by protozoa (T. Scharton-Kersten and A. Sher, Current Opinion in Immunology 9:44-51, 1997). In most instances, cytotoxic activity appears to be dependent upon lymphokine activation (T. Scharton-Kersten and A. Sher, 1997).
NK cells have been implicated as mediators of host defenses against infection in humans with varicella zoster, herpes simplex, cytomegalovirus, Epstein-Barr virus, hepatitis B, and hepatitis C viruses (D. See et al., 1997). Many viruses induce NK cell cytotoxicity, including herpesvirus and cytomegalovirus (C. Biron, Current Opinion in Immunology 9:24-34, 1997). The induction of NK cell activity is a result of the induction of IFN-γ by viral infection, and NK cells are important in the early defense against many viral infections (C. Biron, 1997). The NK1+CD3− population of NK cells is the subset activated by viral infection (C. Biron, 1997). The response of NK cells to viral infection involves direct cytotoxicity and production of various cytokines such as IFN-γ and TNF-α (C. Biron, 1997).
A number of human lymphoproliferative disorders of NK cells are known. These include NK cell-lineage granular lymphocyte proliferative disorder (NK-GLPD), NK cell lymphoma, and acute leukemia of NK cell lineage (K. Oshimi, International Journal of Hematology 63:279-290, 1996). Most patients with aggressive type NK-GLPD die of the disease (K. Oshimi, 1996). NK cell lymphoma is resistant to combination chemotherapy (K. Oshimi, 1996).
NK cells activated with IL-2 have been shown to have activity against human leukemia cells (L. Silla et al., Journal of Hematotherapy 4:269-279, 1995). Furthermore, NK cells appear to have a role in the treatment of chronic myeloid leukemia (K. Oshimi, 1996).
NK cells are involved in both the resistance to and control of cancer spread (T. Whiteside and R. Herberman, Current Opinion in Immunology 7:704-710, 1995). Furthermore, the presence and activation of NK cells may be outcome determinative; low or non-existent NK activity is associated with a high frequency of viral disease and cancer (T. Whiteside and R. Herberman, 1995).
In view of the important role that NK and T cells play in vivo, in host defenses, tumor cell surveillance, and autoimmune diseases, there exists a need in the art for polypeptides suitable for the in vivo and in vitro enhancement of NK and T cell activity.
3. Interferon γ
The production of IFNγ is a function of T cells and NK cells, and IFN-γ activates antiviral immune reactions (E. De Maeyer and J. De Maeyer-Guignard, in The Cytokine Handbook, A. W. Thompson (ed.), Academic Press, 1994, pp. 265-288). IFN-γ preferentially inhibits Th2 proliferation, but not Th1 proliferation (T. F. Gajewski and F. W. Fitch, J. Immunology 140:4245-4252, 1988). IFN-γ also plays an important role in macrophage activation and promotes proliferation of activated B cells (De Maeyer and De Maeyer-Guignard). These, and other effects of IFN-γ, indicate that increased in vivo levels of IFNγ production serve as a general immune modulator.
IFN-γ has been used clinically in treating chronic granulomatous disease, atopic dermatitis, systemic achlerosis, lepratmatous leprosy, common warts, hepatitis B infection, myelogenous leukemia, and metastatic melanoma (J. Mordenti et al., in Therapeutic Proteins, A. H. C. Kung et al. (eds.), W.H. Freeman and Co., 1993, pp. 187-199). In view of the important role that IFN-γ plays, in vivo, in immune modulation, there exists a need in the art for polypeptides suitable for the enhancement of in vivo and in vitro IFN-γ levels.
4. Cytotoxic T Lymphocytes
CTLs are an important in vivo defense against viral, and bacterial, and cancerous diseases, in that they lyse target cells bearing foreign antigens (G. Berke, in Fundamental Immunology, W. E. Paul (ed.) Raven Press Ltd., 1989, pp. 735-764. In view of the important role that CTLs plays, in vivo, in the immune response to infections and tumor surveillance, there exists a need in the art for polypeptides suitable for the enhancement of in vivo and in vitro CTL activity.